This invention pertains to a demineralizer which has improved the reliability of pure water produced.
In general, pure water is made mainly by any of the following three methods, namely, a distillation method, an ion exchange method, and a reverse osmosis method.
In the distillation method, raw water is boiled by heating and the resultant steam is cooled and condensed into pure water.
In the ion exchange method, raw water flows through the ion exchange resin and removed the resolved ionic substance, resulting in pure water. In the reverse osmosis method, raw water is filtered through a molecular level, using a special semipermeable membrane.
In the conventional pure water production devices, the pure water production units provided to treat raw water by any of the above three pure water production methods are used appropriately in two or more sets of combination according to the condition of water to be treated.
In these conventional pure water production devices, however, only the purity of pure water finally obtained is examined by its electric conductivity. If the result of this examination is lower than the predetermined purity level, the pure water is discarded. That is, when there is a pure water production unit which has exceeded the limit of damage orservice available in the raw water treatment process, no means of detecting such damage or service limit is available, making it impossible to immediately replace the unit. Consequently, such production of pure water that must be disused would be continued. As the result, pure water of a desired purity cannot be obtained, making it impossible to improve the reliability of the production unit.